1. Field of the Invention
The invention relates to a control device and control method for an internal combustion engine.
2. Description of Related Art
In an existing art, a vehicle that is driven by an, internal combustion engine includes an exhaust gas purification catalyst and an air-fuel ratio sensor in an exhaust passage of the internal combustion engine, and includes a control device that brings an air-fuel ratio of the internal combustion engine close to a stoichiometric air-fuel ratio on the basis of a detected result detected by the air-fuel ratio sensor such that exhaust gas purification performance in the exhaust gas purification catalyst improves.
Generally, a fuel supply device that supplies fuel into a combustion chamber of an internal combustion engine is installed in a vehicle. The pressure of fuel in a fuel tank is increased to a predetermined fuel pressure by the fuel supply device, and the fuel is supplied into the combustion chamber of the internal combustion engine. In the fuel supply device, as the internal combustion engine stops, fuel that is accumulating in the fuel supply device near the combustion chamber becomes a high temperature, so vapors may be produced in the fuel. Therefore, in the case where the internal combustion engine restarts while vapors have been produced in the fuel in the fuel supply device, when the control device executes air-fuel ratio feedback control, the amount of fuel that is supplied into the combustion chamber deviates from a target amount of fuel, so feedback becomes instable, which may influence fuel economy and exhaust gas characteristic. Then, there is known a control device for an internal combustion engine, which, when vapors have been produced in fuel in a fuel supply device during a stop of the internal combustion engine, stops air-fuel ratio feedback control at the time of a restart of the internal combustion engine (for example, see Japanese Patent Application Publication No. 63-170533 (JP 63-170533 A)).
The existing control device for an internal combustion engine, which is described in JP 63-170533 A, increases a fuel injection amount with respect to a usual fuel injection amount after a start of the internal combustion engine, and stops air-fuel ratio feedback control for a predetermined period of time from the beginning of the start of the internal combustion engine.
With this configuration, the control device for an internal combustion engine, described in JP 63-170533 A, increases the fuel injection amount with respect to the usual fuel injection amount immediately after a start of the internal combustion engine, so vapors are promptly removed from the fuel supply device, and, in a situation that a variation in air-fuel ratio may occur due to supply of fuel containing vapors to the internal combustion engine, the control device, delays a start of air-fuel ratio feedback control and, after vapors are sufficiently removed from the fuel supply device, executes air-fuel ratio feedback control. By so doing, it is possible to stably restart the internal combustion engine.
However, in the above-described existing control device for an internal combustion engine, described in JP 63-170533 A, at the stage of a restart of the internal combustion engine, execution of air-fuel ratio feedback control is stopped, and an increase in the amount of fuel is continued. After that, fuel may be excessively supplied to the internal combustion engine, and there is a case where the air-fuel ratio significantly deviates toward a rich side at the time of a restart of the internal combustion engine. Therefore, in the control device for an internal combustion engine, described in JP 63-170533 A, there is a problem that fuel economy deteriorates or exhaust gas characteristic deteriorates.
In addition, in the above-described existing control device for an internal combustion engine, described in JP 63-170533 A, if an increase in the amount of fuel at the time of a restart of the internal combustion engine is performed without stopping executing air-fuel ratio feedback control at the time of a restart of the internal combustion engine, the air-fuel ratio deviates toward a rich side, so the fuel injection amount reduces such that the air-fuel ratio is corrected toward a lean side through air-fuel ratio feedback control. When fuel injected into the combustion chamber contains large amounts of vapors in this state, the amount of fuel that is supplied to the internal combustion engine may become smaller than a minimum amount that is required to maintain the rotation of the internal combustion engine and, as a result, engine stalling may occur.